Process of separating a liquid into its constituent parts



Oct. 13, 1936. p SCHUFTAN AL 2,057,598

PROCESS OF SEPARATING A LIQUID INTO ITS CONSTI'I'UENT PARTS Filed Oct. 23, 1934 w 5 Sheets-Sheet l 0a. 13, 1936. P. SCHUFTAN ET AL PROCESS OF SEPARATING A LIQUID INTO ITS CONSTITUENT PARTS Filed Oct. 23, 1934 3 Sheets-Sheet 2 Oct. 13, 1936. p SCHUFTAN ET AL 2,057,598

PROCESS OF SEPARATING A LIQUID INTO ITS CONSTITUENT PARTS Filed Oct. 25, 1934 3 Sheets-Sheet 3 3mm: PM! JW WJM Patented Oct. 13, 1936 'UNITE STATES PATENT .OFFICE rnocess orisrmm'rmc A mourn m'ro ITS CONSTITUENT PARTS Paul 'Schuftan, Hollriegelskreuth, near Munich,

Ernst Karwat, Grosshesselohe, near Munich, and Albrecht Steinbach, Wiesbaden, Germany Application October 23, 1934, Serial No. 149,668

. In Germany November 1,1933

12 Claims. (CL 62-124) This invention relates to a process for resolving solutions and liquid mixtures into their constituents by crysallizing and separating individual constituents thereof.

It is known to'separate and recover constituents of solutions by converting either the solute or the solvent into the solid condition and then separating the solid and liquid phases. In.this manner salts can be deposited from solutions, and concentrates can be produced from liquids (such as 'milk) by freezing out the contained water. For the latterpurpose in particular, it

has been proposed either to. transform the liquidinto a more or less compact "pulp of ice crystals by cooling accompanied by agitation, or to freeze the liquid into blocks and then crush the blocks Denying drawings which illustrate and then separate the ice from the mother liquor,

for example by centrifuging.

The present invention contemplates a process -for resolving solutions into their constituents which is substantially simpler in operation than the processes hithertosuggested. To this end, according to the invention, the liquid to be resolved is cooled in,a. vessel of a shape adapted to that of the apparatus employed for separating the solid and liquid phases, the cooling being carried to suchan extent that a structurally stable body that is to say,-'a solid body which retains its shape, is-obtained which can be directly inserted into the separator and further treated therein.

The temperature gradient during the cooling periments have shown that, in such case, the

separation, so that a particularly easy and ef-.

fective separation of the liquid and solid phases results. The lowest temperature attained in cooling must be above the eutectic temperature of the constituents to be separated, since otherwise, complete separation of the constituents is fundamentally impossible. Nevertheless, in certain circumstances, for example when a high rate of cooling is desired, a partial descent below the eutectic temperature moulded body be correspondingly warmed prior to the separation of the two phases.

The process. of the present invention will hereinafter be more fully described as applied to the production of a milk concentrate by freezing out the water and then separating the concentrate from the ice, and with reference to the'accom-.

is permissible, if s the- -centrifuge 23 (Fig. '6).

: u tically and by way of example various embodiments of apparatus suitable for carrying the present invention into practical effect, and in which:-

Figs. 1 and 2 are respectively a transverse sec-' tion and a' top plan view of a refrigeration cell;

Fig. 3 is a longitudinal section through a refrigerating apparatus embodying a plurality of refrigeration cells on the line 3-3 of Fig. 4; Fig. 4 is a top plan view of Fig; 3;

Fig. 5 is a section through a second embodiment of refrigerating apparatus; and

Fig. 6 is a front elevation withparts broken away showing the interior in section, of a centrifugal apparatus for the treatment of the ice masses produced in the-refrigeration cells.

In carrying out the invention, the milk after having been freed from gas-if desired by evacuationis cooled in a circular annular vessel 5, m the internal diameter and height of which correspond to the dimensions of the basket 24 of the It has been ascertained that,- under these conditions, the ice is deposited in the form of acicular,. or'lamelliform crystals, 25 which are practically all orientated in the direction of the steepest temperature gradients, namely in the radial direction of the annular vessel I, the concentrate accumulating, at the same time, in the radially disposed interstices and 30 channels between the ice crystals. The. cooling process is continued until the desired amount of ice.has been precipitated, or at least to such an extent that the ice skeleton formed in the refrigeration vessel l is sufliciently strong to allow 35 the mixture of ice and concentrate to be transferred to the centrifuge 23 without collapsing.

On the termination of the cooling process, the

annular block of ice is taken out of the ref i eration vessel I, if necessary after warming the 40,-

' can be easily removedyby the vessel,

without the milk becoming contaminated with the freezing brine. A slightly different method 50 of. extracting the frozenblock consists in allowing hooks or carriers 2 (Figs; 1, 2 and 6) to freeze into the ice, and employing such devices for withdrawing the moulded body and transferring it. to the centrifuge. o6.

v grow at the edges andrims of the annular ice centrifugal forces generated act in exactly the same direction as that in which the interstices between the crystals'which-are occupied by the concentrate, are disposed. Consequently, in the herein-described process, the concentrate is readily and extensibly separated from the ice, where-- block, from which the concentrate is difiicult .to expel, the, transition of heat, and thus the rate of growth of such crystals, can be reduced, by

.the provision of heat-insulators 3, (Figs. 1 and 2) at these places, so as to preventthe occurrence of this source of trouble.-

By operating in the herein described manner, relatively compact ice is obtained, in thin strata- The exhibiting narrow intermediate channels. ice has a temperature, below 0., corresponding to a state of equilibrium with the concentrate. When moisture now penetrates intothe narrow -channels--for example as the result of the in-- terior surface of the ice block becoming partially melted by' th'ewarm air agitated by the I centrifuge-the water freezes in the channels of the still colder interiorof' the iceblock, thereby choking said channels and rendering impossible further separation of ice and-concentrate. this account, in carrying out the invention, any warming of the inner surfaces of the'ice block in the centrifuge is prevented, for example by employing an'annular cage--si milar to thereso that the stripping liquid in the channels can- 55 frigeration vessel-the inner wall. 25 of the cagebeing solid and thus keeping the ice .ring out of contact with air.

A- sinteringeffect; however, may beexerted, for. the same reasons, on theice block by the Washing liquid. This difiiculty is. overcome by using instead .of pure water, in the first washing, .a solutionthe concentration of which is adapted to the temperature of theice-for the timev being,

not freeze. To this end, use. is made, for ex- .ample, ofprogressively more dilute solutions,

" I sprayedon to'the ice through an atomizer nozzle' 21-. When the ice has reached 0C., it may be washed with -pure water, if desired. This method of stripping the ice can be combined in a simple. manner, with the. protection against sinter'i'ng, by allowing a pre-cooled gas, more particularly'air, to flowover the inner wall of the ice ring. The'temperature of the gas during the centrifuging of the concentrate, is approximately'the same as the melting temperature of the ice-for the time being. For the purpose of the stripping operation, its temperature is gradually raised in the desired degree, so that small quantities of ice water areformed, which, at-

the outset, form with the dry substances adher'ing to the ice a concentrated solution which becomes progressivelymore dilute, as the result of the stripping, during the process.

The centrifuged ice block is preferably other of the pipes.

, 2,067,598 In the subsequent centrifuging process, the.

moved from the centrifuge conjointly with the interchangeable sieve or carrier 2, and is melted by direct or indirect heat exchange with the refrigerating medium.

In order to shorten the Yfreezingperiod and also to ensure the most complete separation of the concentrate. 'from the ice in centrifuging, the width of the annular refrigeration vessel should not exceeda few centimeters. In order further to increase thetransmission of heat between the .refrigerating'medium, and the milk, the refrigeration vessel is moved in relation to the refrigerating medium-for example by rotation on its axis--on the one hand, and on the other hand a moderate movement towards the refrigerating walls is imparted to the milk. In

particular, a movement havinga powerful vertical component, is imparted to the refrigerating liquid, so that, in the main, it flows in a vertical direction along the walls of the refrigeration vessel.

will hereinafter be more fully explained, with reference to Figs. 3 to 5;

In Fig. 3, ll represents the refrigerating tank for the cells, said tank being cooled, for example by the evaporation of a refrigerating liquid, such .The cooling of the annular refrigeration cells as ammonia, in the pipes H2. The wall 5 has an opening forthe' propeller l3 and other openings from which the pipes 15 project upwardly. The annular freezing vessel I is positioned so that it surrounds one of the pipes I5 and lies' between In operation the cooling liquid flows down through thepropeller [3, over the pipe l2, up through pipes.l-5 .and out of the open endsthereof, down over both the inner and outer' walls of the freezing vessel l, and back Ito the distributing pipes 18 and I9, by which it oration cell I, then runs down the latter, is col-- lected in the vessel 21 and then returned to the brine cooler by the pump 22. this method is that the amount of brine-to be kept in circulation is substantially less than in fore possible toadapt the brine temperature to the momentary freezing temperature in the cells, during the stages of the process. Moreover, the

expensive cell. tanks otherwise required can be replaced by a simple wooden enclosure.

A' somewhat different method: consists insetting the" cells inrotation and providing spiral stages or. strips' on the interior -wall and-if. de-

sired also on the ,outer wall of the cells, which of the herein described new level cooling tank, through the pipes I 6 and I],

' is sprayed against the upper edge of the refrig The advantage of the case of the usual cell tanks, and it is there- I process are that the operation is simplified and the apparatus substantially. cheapened. In contrast to the processesoperating by imparting chanical stressing of the walls is absent, so that weaker wall material, such as enamel, can' be 76 movement to-the material. to be cooled, the me- I accuse g 1 3 scraped oil! from the walls or. stirrer-s, .on the phase by subjecting the mass to centrifu l force.

- ,fiavour of sensitive substances, such as milk and 5. A process for the separation of the .con-

fruit juices, is prevented. Bycomparison with stituerits of liquids as defined in claim 1 in.

. the processes in which'the solution to'be concenwhich the mass has two substantially parallel 5 trated is frozen to a'block. the latter being then? faces and the liquid phase thereof is separated, 6 crushedand further treated in a centrifuge, the by forcinga fluid through the mass in the direcnewprocess offers the advantage that the freeztion perpendicular to said faces. in'g period is sulwtantially reduced, one working 6. Process for the separation of the constitustage "is saved,- the purity of the product being cuts of liquids as defined in claim 1 in which 10 thereby improved and the loss of cold and subin cooling the body of liquid a temperature '10 stance lessened. Furthermore, as the result of gradientis' maintainedin a predetermined dithe orientationof the crystals, theseparation of rection through said body whereby an orientathe two phases can be carried out with the same tion -'of the resulting solid phase of the mass expenditure of labour and with an improved in said direction is produced and in which, in v yield. the separation of the solid and liquid phases, l5- The invention is obviously not restricted to the the force for displacing the liquid phase is-applied foregoing example of concentrating milk, but can in said direction. a be similarly applied to the concentration of other '7. Process for the separation of the constituliquids, especially such as are sensitive to fiavour- .ents of liquids as defined in claim 1 in which an ing influences. It can also be applied tothe annular-body of liquid is converted into an an- 20 purification of dissolved substances, suchvas annular' structurally stable mass by maintaining hydrous acetic acid, or salts.- I a temperature gradient radially of said-body and It is moreover immaterial for the purposes of in which the force serving to separate the liquid the present invention whether the separation of phase from the solid phase of the mass is applied the solid and liquid phasesbe performed in aradially thereof. 7

' centrifuge. The only essential feature is to pro- 8. Procas for the separation of the constituduce, by refrigeration, amoulded bodythat can ents of liquids as defined in claim 1 in which an be directly transferred into the separating deannular body of liquid is transformed'into an vice, and that the cooling is performed in such annular structuralLv stable mass and the liquid I a manner. that theorlentation of the crystals phase of said mass is separated from the solid 30 "coincides the direction of the forces eflectphase by centrifugal force acting radially of ing the-separation: of the two phases. Thus, for said example when filters are employed for separating 9. Process for the separation or the constituthetwophases, the moulded body is shaped as a ents of liquids as defined in claim 1 inwhich a corresponding to the-filter, said disc bein body of liquid having'at least two substantially 35 cooledfrom the end surfaces'in such a manner parallel faces is transformed into a structurally that the crysigls and the channels containing stable mass by cooling while maintaining a r the mother liquor are orientated at right; angles temperature gradient between said faces perpen=----' to said'surfaces and therefore in the direction of dicular theretmand in which the, liquid phase is the suction efiort of the filter. V 1 sepmatedfrom the solid phase by force applied we claim: n perpendicular to said parallel faces.

1. A process for theeparation of the con- 10. Process for the separation of the constitu= stituentsof liquids whichcomprises transformcuts of 'liquidsasdefinedin'claimd inwhicha ,ing a body of a liquid by cooling into a struc turalwlbndy-of liquid having at least two substantially ly stable massofthe sameshapeas'said body of parallel faces is transformed into a structurally 4 liquidsaid mass comprising a solid and a liquid stable mass by cooling while maintaining a tem- H a I phase, and applying force to said mass without peijaturegradient between said faces perpendicw -dislntegration'thereof' for the separation of' said lar thereto, and in which the liquid phase is solid and liquid phases. separated from the solid phase by forcing a .2. A process for the separation of the con-- fluid through the mass in a directionperpen- 50 stituents of liquids as defined in claim 1 in dicular to said faces. which. the-solid and liquid'phasesof said mass 11. A process for the. separation ofthe-conare separated by subjecting the massto centrifstituents of liquids as defined in claim 1 in which u'galforce. 'the mass is washed with a liquid which will not '55. 3. A process for the separation of the consolidifyat thetemperatura of the mass.

- stituents of liquids as defined-in claim 1 in 12. A process for the separation of the conwhichithe solid and liquid phases of said mas 'stit uents' of liquids as defined in claim 1 in which aTreseparated by forcing a fluid said a stream ofgas at a slightly higher temperature mass. 1 than the mass is contacted therewith.

' 4.-A process for the separation of the con-. 60 stituents of liquids as defined in 1- in V PAUL SCHUFTA which the mas is annular in shape and in which ERNST KARWAT.

' .the liquid phase is separated from thesolid. 'srsmnacn. 

